17-115 Pavel Exner and Sylwia Kondej
Aharonov and Bohm vs. Welsh eigenvalues (167K, pdf) Dec 13, 17
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Abstract. We consider a class of two-dimensional Schr\"odinger operator with a singular interaction of the $\delta$ type and a fixed strength $eta$ supported by an infinite family of concentric, equidistantly spaced circles, and discuss what happens below the essential spectrum when the system is amended by an Aharonov-Bohm flux $lpha\in [0, rac12]$ in the center. It is shown that if $eta e 0$, there is a critical value $lpha_\mathrm{crit}\in(0, rac12)$ such that the discrete spectrum has an accumulation point when $lpha<lpha_\mathrm{crit} $, while for $lpha\gelpha_\mathrm{crit} $ the number of eigenvalues is at most finite, in particular, the discrete spectrum is empty for any fixed $lpha\in (0, rac12)$ and $|eta|$ small enough.

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